Aetna CEO: Obamacare In A 'Death Spiral' Heading Into 2018. Aetna and Humana have called off their deal amid government concerns over competition. Here's a look back at six pivotal moments that led to this. Aetna and Humana have called off their deal amid government concerns over competition.
For the plant genus, see Synapsis (plant). Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis.
A synapse includes a presynaptic portion (synaptic ending), a synaptic cleft, which separates two cells, and a postsynaptic portion, which is the part of a cell adjacent to a synaptic ending.xcitatory or inhibitory effects in a synapse with a chemical reaction are produced by a series of processes. The nerve impulse, upon arriving at a presynaptic ending, depolarizes the presynaptic membrane, whose permeability to calcium ions is increased.